Ultrasonographic Features of Lower-Limb Joints in Gout: Which Joints and Clinical Characteristics Would Provide More Information for Diagnosis?

OBJECTIVE: This observational cross-sectional study evaluated the distribution of ultrasound (US) features of lower-limb joints and the risk factors of tophus in gout patients. METHODS: We examined 588 joints including the bilateral knee, ankle, and first metatarsophalangeal (MTP) joints in 98 gout patients by US between March to August in 2017. The distribution of double-contour (DC), tophus, aggregates, synovitis, effusion and erosion in different joint, course, and age groups were investigated by Cochran Q and χ test. The risk factors of tophus were analyzed using logistic regression method. RESULTS: Double-contour was most commonly observed in the knee (p = 0.005). Tophus, aggregates, synovitis, and erosion were mostly detected in the first MTP (p < 0.001, p = 0.01, p = 0.001, p < 0.001, respectively). The prevalence rates of DC, tophus, and erosion in patients with a longer course were significantly higher (p = 0.029, p = 0.002, p < 0.001, respectively). Older patients had more detectable tophus and erosion than younger patients (p = 0.028, p = 0.021). Patients of older age (odds ratio [OR], 3.83; 95% confidence interval [CI], 1.27-11.48), with frequent attacks (OR, 3.80; 95% CI, 1.10-13.15), and with longer course (OR, 6.52; 95% CI, 1.37-30.96) had higher risks of tophus. CONCLUSIONS: Most signs were detected by US in the first MTP, except that DC was most commonly observed in the knees. Patients of older age with frequent attacks and longer course may experience higher risks for tophus. Comprehensive assessment of the lower limbs, particularly the knee and first MTP, can significantly help diagnosis.